feat(CaptionStream): add flag to turn off 708 captions (#365)

Pass `parse708captions` to transmuxer or CaptionStream to turn off parsing for 708 captions.

Author: gkatsev

lib/flv/transmuxer.js

@@ -373,7 +373,7 @@ Transmuxer = function(options) {
     .pipe(this.metadataStream)
     .pipe(coalesceStream);
   // if CEA-708 parsing is available, hook up a caption stream
-  captionStream = new m2ts.CaptionStream();
+  captionStream = new m2ts.CaptionStream(options);
   h264Stream.pipe(captionStream)
     .pipe(coalesceStream);
 

lib/m2ts/caption-stream.js

@@ -20,10 +20,16 @@
 var Stream = require('../utils/stream');
 var cea708Parser = require('../tools/caption-packet-parser');
 
-var CaptionStream = function() {
+var CaptionStream = function(options) {
+  options = options || {};
 
   CaptionStream.prototype.init.call(this);
 
+  // parse708captions flag, default to true
+  this.parse708captions_ = typeof options.parse708captions === 'boolean' ?
+    options.parse708captions :
+    true;
+
   this.captionPackets_ = [];
 
   this.ccStreams_ = [
@@ -33,7 +39,9 @@ var CaptionStream = function() {
     new Cea608Stream(1, 1) // eslint-disable-line no-use-before-define
   ];
 
-  this.cc708Stream_ = new Cea708Stream(); // eslint-disable-line no-use-before-define
+  if (this.parse708captions_) {
+    this.cc708Stream_ = new Cea708Stream(); // eslint-disable-line no-use-before-define
+  }
 
   this.reset();
 
@@ -44,9 +52,11 @@ var CaptionStream = function() {
     cc.on('done', this.trigger.bind(this, 'done'));
   }, this);
 
-  this.cc708Stream_.on('data', this.trigger.bind(this, 'data'));
-  this.cc708Stream_.on('partialdone', this.trigger.bind(this, 'partialdone'));
-  this.cc708Stream_.on('done', this.trigger.bind(this, 'done'));
+  if (this.parse708captions_) {
+    this.cc708Stream_.on('data', this.trigger.bind(this, 'data'));
+    this.cc708Stream_.on('partialdone', this.trigger.bind(this, 'partialdone'));
+    this.cc708Stream_.on('done', this.trigger.bind(this, 'done'));
+  }
 
 };
 
@@ -213,7 +223,9 @@ CaptionStream.prototype.setsTextOrXDSActive = function(packet) {
 };
 
 CaptionStream.prototype.dispatchCea708Packet = function(packet) {
-  this.cc708Stream_.push(packet);
+  if (this.parse708captions_) {
+    this.cc708Stream_.push(packet);
+  }
 };
 
 

lib/mp4/transmuxer.js

@@ -982,7 +982,7 @@ Transmuxer = function(options) {
     pipeline.timestampRolloverStream = new m2ts.TimestampRolloverStream();
     pipeline.adtsStream = new AdtsStream();
     pipeline.h264Stream = new H264Stream();
-    pipeline.captionStream = new m2ts.CaptionStream();
+    pipeline.captionStream = new m2ts.CaptionStream(options);
     pipeline.coalesceStream = new CoalesceStream(options, pipeline.metadataStream);
     pipeline.headOfPipeline = pipeline.packetStream;
 

lib/partial/transmuxer.js

@@ -30,7 +30,7 @@ var tsPipeline = function(options) {
       timestampRollover: new m2ts.TimestampRolloverStream(),
       adts: new codecs.Adts(),
       h264: new codecs.h264.H264Stream(),
-      captionStream: new m2ts.CaptionStream(),
+      captionStream: new m2ts.CaptionStream(options),
       metadataStream: new m2ts.MetadataStream()
   };
 

test/caption-stream.test.js

@@ -883,7 +883,7 @@ QUnit.test('clears buffer and drops data until first command that sets activeCha
   assert.equal(captions[1].stream, 'CC4', 'caption went to right channel');
 });
 
-QUnit.test('ignores CEA708 captions', function(assert) {
+QUnit.test("don't mess up 608 captions when 708 are present", function(assert) {
   var captions = [];
   captionStream.ccStreams_.forEach(function(cc) {
     cc.on('data', function(caption) {
@@ -902,6 +902,48 @@ QUnit.test('ignores CEA708 captions', function(assert) {
   assert.equal(captions[2].text, 'WE TRY NOT TO PUT AN ANIMAL DOWN\nIF WE DON\'T HAVE TO.', 'parsed third caption correctly');
 });
 
+QUnit.test("both 608 and 708 captions are available by default", function(assert) {
+  var cc608 = [];
+  var cc708 = [];
+  captionStream.on('data', function(caption) {
+    if (caption.stream === 'CC1') {
+      cc608.push(caption);
+    } else {
+      cc708.push(caption);
+    }
+  });
+
+  var seiNals = mixed608708Captions.map(makeSeiFromCaptionPacket);
+  seiNals.forEach(captionStream.push, captionStream);
+  captionStream.flush();
+
+  assert.equal(cc608.length, 3, 'parsed three 608 cues');
+  assert.equal(cc708.length, 3, 'parsed three 708 cues');
+});
+
+QUnit.test("708 parsing can be turned off", function(assert) {
+  captionStream.reset();
+  captionStream = new m2ts.CaptionStream({
+    parse708captions: false
+  });
+  var cc608 = [];
+  var cc708 = [];
+  captionStream.on('data', function(caption) {
+    if (caption.stream === 'CC1') {
+      cc608.push(caption);
+    } else {
+      cc708.push(caption);
+    }
+  });
+
+  var seiNals = mixed608708Captions.map(makeSeiFromCaptionPacket);
+  seiNals.forEach(captionStream.push, captionStream);
+  captionStream.flush();
+
+  assert.equal(cc608.length, 3, 'parsed three 608 cues');
+  assert.equal(cc708.length, 0, 'did not parse any 708 cues');
+});
+
 QUnit.test('ignores XDS and Text packets', function(assert) {
   var captions = [];